The purpose of this paper is to provide an overview of assessment, diagnosis, and treatment planning for individuals with substance abuse problems. The intent is to provide information to professional counselors in school, rehabilitation, school psychology, social work, public mental health, and private treatment settings. Information to be obtained in a comprehensive assessment includes: developmental aspects of adolescence; external influences such as family and peer groups; diagnostic information relating to etiology and prognosis; and recommendations and considerations related to a treatment plan. Several dual diagnoses specifically associated with drug abuse are discussed including depression, conduct, anxiety/panic, substance induced anxiety, and eating disorders. A structured diagnostic interview is presented for use in obtaining information for managed care and other third parties. Also included is a facilitator's manual which is a practical guide for teaching content through guided experiential projects. Four objectives are listed, and four student exercises are provided. (Contains 27 references.) (MKA)